The invention relates to a method for receiving broadcast signals in a vehicle and a broadcast receiving apparatus designed for performing the method, in particular for use in a motor vehicle. It is provided in the method proposed according to the invention that there are available a plurality of reception paths for a broadcast receiver in order to receive and computationally process broadcast signals separately from one another. This operating principle of broadcast receivers is generally known and therefore not described in greater detail.
In addition, a plurality of playback devices can each be connected to one or more reception paths in order to play back received broadcast signals, wherein a plurality of reception paths can be combined for one playback device in order to improve the reception quality.
The reception conditions of broadcast receivers for radio systems such as VHF, shortwave, medium wave, longwave, Digital Radio Mondiale (DRM), Digital Audio Broadcasting (DAB), Digital Video Broadcasting (DVB) or the like are normally impaired by multipath reception. The reason for this lies in frequency-selective and time-selective fading, which is caused by scattering objects, both stationary and moving, and by the broadcast receiver that itself is moving. Examples of scattering objects are mountains, trees, buildings and/or other vehicles. Such broadcast receivers are found in television equipment and/or radio equipment installed in vehicles. These broadcast receivers do not differ fundamentally from broadcast receivers in homes, where they are usually installed as stationary equipment.
It is known in radio systems to provide measures against multipath reception effects and to improve the signal quality. For instance, the Orthogonal Frequency Division Multiplexing technique (OFDM) is known for this purpose, which is performed exclusively in the broadcast receiver. This technique involves signal equalization, radio-channel estimation and signal decoding. These processing steps are also referred to below under the combined term of reception processing.
It is also known that a broadcast receiver uses a plurality of antennas simultaneously, and analyses the signals from these various antennas. This procedure is known as diversity, and has the advantage that by suitable superposition (e.g. phase diversity) of the individual antennas, which have a different signal quality from one another depending on the arrangement and vehicle orientation, it is possible to achieve a better reception quality overall than by using only a single antenna. Alternatively, it is also possible to select the antenna for reception that delivers the best signal quality at that moment (e.g. scan diversity).
It is also known that broadcast receivers use a plurality of reception paths, in which separate computational processing of the received signals takes place. This computational processing is then re-combined in a processor or even in a higher-level processor in order to produce a playback signal of higher quality overall. This procedure is also referred to as separate baseband processing, using the respective reception paths and subsequent combining of the various received signals.
The broadcast receiver normally combines the various received signals in a fixed manner. In some cases, the reception paths are configured on the basis of usage situations.
Examples of this in a motor vehicle are when the user of a rear-seat unit is watching a television program, and the user of a head-unit is not watching a television program. In this case, depending on the resources available, i.e. in particular the number of reception paths available, one reception path can be used for a background search for additional stations, which can then be offered to the user during a change in station. If both the user of the rear-seat unit and the user of the head-unit are watching a television program, all the reception paths are used for this purpose. Then there is no longer a reception path available for a background search for additional stations.
The term “resources” is used in the present disclosure in particular to cover all the hardware elements and software modules involved in a reception path.
In addition, systems have already been specified for switching dynamically in FM broadcast receivers between phase diversity, scan diversity and diversity being disabled according to the reception quality, which has been defined, for example, as multipath, noise, field strength, RDS, bit error rate and/or similar quantities.
The problem with the prior assignment of the reception paths is that either they have a fixed assignment in a playback device or reception quality measurements must be carried out, which can only be assessed reliably with difficulty because of the frequent variation in received signal qualities, especially in a moving motor vehicle. This leads to high processing complexity and sometimes high levels of switching between different diversity settings and reception paths, with the result that only poor use can be made of temporarily unused reception paths for other functions.
The object of the present invention is therefore to achieve a more effective assignment of reception paths to playback devices.